Study: Noise machines to help babies sleep may damage hearing

Baby ears are sensitive and frequent exposure to white noise could be hazardous to hearing. (Amanda Rohde / Getty)

Today’s parents often use white noise machines to help their babies fall asleep at night, but a new study from the Hospital for Sick Children in Toronto finds that many of these devices produce sound at levels that may be damaging to an infant’s hearing and auditory development.

For the March 3 study published online in the journal Pediatrics, researchers tested 14 infant sleep machines at their maximum operating level and found that all gave off sound exceeding 50 A-weighted db (dbA), the recommended noise limit for hospital nurseries. (A dbA is a unit of sound measure used for assessing potential hearing damage caused by loud noise.) Three devices produced output levels over 85 dbA. If these machines were turned on for eight hours, the sound level would exceed the limit for noise exposure in adult workplaces.

Dr. Blake Papsin, otolaryngologist-in-chief at the Hospital for Sick Children, and his colleagues, tested their sleep machines at three distances: at 30 centimeters to simulate being in the crib or on the rail, 100 centimeters to simulate placement beside the crib, and across the room at 200 centimeters distance from the baby. Even when the device was placed all the way across the room at 200 centimeters, sound levels were at levels that could be dangerous.

Baby ears are still developing and sensitive and frequent exposure to white noise could affect hearing, speech and language development, and could potentially cause possible hearing impairment, the study authors concluded.

“We understand that life gets loud, but to me, it doesn’t make sense to drown out noise with other noise,” the study’s lead researcher Dr. Papsin said in a statement. “We know that parents are trying to do what’s best for their babies and their sleep, so we hope this study informs the public about the potential harms, and educates them on appropriate use of the machine.”

Many parenting experts and web sites encourage parents to use sound machines to play ambient noise while their babies sleep. These machines usually have a variety of sound settings, from “mom’s heart beat” to “ocean waves” to basic “white noise.” Some experts say that babies like these repetitive swishing sounds because they mimic the sounds babies hear in their mother’s womb. What’s more, these machines help mask distracting noise, whether it’s the sound of mom clanging pots in the kitchen downstairs or of cars driving by outside a bedroom window.

As a baby, my first daughter slept in a room looking over a noisy San Francisco alleyway. To mask the cacophony outside her bedroom window, I placed a noise machine near her crib. She seemed to prefer the “ocean waves” setting and we used to joke that the sounds would inspire her to be a great swimmer or marine biologist, when she grew up. But maybe the sounds were actually damaging her tiny developing ears?

Dr. Papsin told National Public Radio that he got the idea for the study when he was visiting a patient at the Hospital for Sick Children. The parents had placed a noise machine next to their child to help him fall asleep and it was giving off sounds so loud that Papsin found it difficult to carry on a conversation. He wondered, Are these machines operating at sound levels that could be hazardous to a child’s hearing?

Since Papsin found that the answer is yes, does this mean parents should toss their noise machines? “It is possible to use these machines safely, but without instructions or device limitations we cannot say that they are being used appropriately by parents,” Dr. Papsin says.

“An informed parent is the best parent…We are simply suggesting that they be used with caution, and other methods, such as lullabies and sound absorbers, be used whenever possible,” he added.

The researchers offered up a few tips for parents using sound machines:

1) Place the device as far away as possible from the infant and never place it inside the crib or on the crib rail.

2) Turn the volume on low.

3) Use the machine for as little time as possible. For example, turn it on at the beginning of the nap, and then turn it off once your baby falls asleep.

The study also recommends that policies are created for manufacturers. Papsin and his team suggested that companies limit the maximum output level, place warning labels about noise-induced hearing loss, and require manufactures to include a mandatory timer with auto shut-off.